The present invention is in a method for the preparation of organosilanes containing methacryloxy or acryloxy groups, which are also referred to hereinafter as acrylosilanes. The method is based on the known reaction of alkali methacrylates or alkali acrylates with chloroalkylsilanes in the presence of quaternary ammonium salts as catalysts.
Japanese patent application 51348/65 discloses that acrylosilanes of the general formula ##STR1## in which R.sup.1 represents a hydrogen atom or a methyl moiety, R.sup.2 an alkyl moiety with 1 to 4 carbon atoms, R.sup.3 alkyl groups with 1 to 4 carbon atoms, m either 0 or 1 or 2, and n a number from 1 to 4, can be prepared by the reaction of solid alkali salts of methacrylic acid or acrylic acid with chloroalkylsilanes of the general formula ##STR2## in which R.sup.2 and R.sup.3 =C.sub.1 to C.sub.4 alkyl groups, m=0 to 2, and n=1 to 4, in the presence of quaternary ammonium salts as solid-fluid phase transfer catalysts.
Triethylamine, dimethylaniline, tetramethyl ammonium chloride and benzyltrimethyl ammonium chloride are named in the Japanese application as phase transfer catalysts. Both of the last-named compounds are used in the examples given in the Japanese patent application for the reaction between the solid phase, consisting of the alkali salt of the methacrylic or acrylic acid, and the liquid phase, consisting of the chloroalkylsilane and the phase transfer catalysts.
High reaction temperatures of 140.degree. C to 180.degree. C are necessary for the performance of the reaction when using the above catalysts. The reaction times can extend up to 6 hours. Moreover, a large excess of chloroalkylsilane, which can amount to 10 times the molar amount of alkali methacrylate or acrylate, is required. Furthermore, additional solvent, such as dimethylformamide, toluene or xylene, must be added.
The organosilane yields in this known method are decidedly less than 90% and often amount to only about 70%. When a molar ratio of alkali (meth)acrylate to chloroalkylsilane is 1:1, the yield is only 65% and the formation of a large amount of polymeric material accompanies the product.
Furthermore, the required high reaction temperatures, the large excesses of chloroalkylsilanes, the additional solvent, and the long reaction times, are all decided disadvantages. High temperatures promote the formation of undesired polymeric products. Long reaction times and large excesses of chlorosilane lead to a considerable reduction of the yield per unit of space and time. Furthermore, the large excesses of chloroalkylsilane and the use of an additional solvent adversely affects the energy balance in the purification of the organosilanes by distillation. Also, the use of an additional solvent adversely affects the yield of the organosilanes.
The problem therefore existed of conducting the reaction between alkali (meth)acrylates and chloroalkylsilanes with the formation of acrylosilanes such that it would be possible to operate at low reaction temperatures, obtain a higher yield per unit of space and time, and minimize the percentage of polymeric products.